Self-locking ntt



Jan. 5, 1943.

H. F. GADE SELF-LOCKING NUT Original Filed Oct. 22, 1941 Reissues] Jan. 5, 1943 SELF-LOCKING NUT nmua F. Gade, Philade1phia, Pa., assignor to Pennsylvania Manufacturing Company, Jenkintown, Pa., a corporation of Delaware Original No. 2,290,175, dated July 21, 1942, Serial No. 416,121, October 22, 1941.

Application for reissue November 4, 1942, Serial No. 464,500

. 4 Claims.

This invention relates to self-locking nuts of the type disclosed in my co-pending application Serial No. 393,824.

The principal object of the present invention is to provide an improved method for manufacturing nuts of that type.

The nuts to which the invention pertains are provided at one end with aplurality of locking segments which are formed so as to constrict the normal bore of the nut and which are resiliently displaceable in the radial direction, so that when the nut is applied to the companion bolt, the segments will exert a resilient pressure against the sides of the bolt to lock the nut in place. Conventionally, the inner threaded faces of the segments are formed on an are having the same radius as the normal bore of the nut, and the side edges of the segments have a tendency to scrape the surfaces oi the bolt, which is undesirable, particularly where the bolt. and nut are coated or plated with cadmium or other rust-inhibitingmaterial. In such cases, the scraping action of the side edges of the locking segments will sometimes remove the protective coating and expose the ferrous metal or the bolt to oxi-, dation.

In my aforesaid application, a means was described for avoiding this undesirable characteristic by increasing the radius 01 curvature of the inner faces of the locking segments, so that the side edges of the segments were removed from direct contact with the bolt. The present invention aflords a more economical method of achieving the same result.

In the attached drawing,

Figure 1 is a side elevational view of a nut made in accordance with my invention;

Figure 2 is a top plan view of the nut;

Figure 3 is a sectional view illustrating the nut in an early stage of manufacture;

Figures 4 and 5 are corresponding sectional views illustrating subsequent steps in the process of manufacture;

Figure 6 is a top plan and partial sectional vie: showing the finished nut applied to a bolt, an

Figures 7 and 8 are views illustrating may be used in production.

With reference to Figs. 1 and 2 01' the drawing, the nut therein illustrated as an embodiment of the invention is provided at its upper or outer end with a plurality of segments l which may be tools that iormed by slotting the body of the nut longiv tudinally and radially from said upper'end as indicated at 2. Preferably, the segments i are under-cut at the outside of the nut, so that they are joined to the body 3 of the nut by a relatively small section 4 of metal, thereby affording the iii! segments a suitable degree of resiliency in the radial direction consistent with their locking function as hereinafter set'iorth.

In producing this nut in accordance with the present invention, the nut blank of the desired form. such, for example, as that shown in Fig. 1, may be slotted at one end to provide the k'erfs 2 which define the sides of the several locking segments. The blank may then be tapped in the usual manner to provide the thread of desired pitch and pitch diameter. Preferably, the slotting of the nut precedes the tapping operation, although these two steps may be reversed without departure from the invention. In either case, I have found it desirable, after the tapping and slotting operations, to pass the nut onto and over a threaded mandrel 3, see Fig. I, having a corresponding thread, the purpose of this operation being, in effect, to work in the thread and to remove the burrs which may exist as a result of the slotting and threading operations In this operation, the nuts may be fed successively over the length of the threaded portion ill of the mandrel and from the threaded portion onto the unthreaded shank H from which the nuts may readily be removed. In lieu of the mandrel 9, an elongated tap I2 may be used, of the general form illustrated in Fig.8, the nuts being passed over, the extended threaded portion of the tap in the manner described above and onto the unthreaded shank for subsequent removal.

Following the slotting and tapping operations, described above, and in accordance with the present invention, I then re-tap the segmented end of the nut to a point, preferably, slightly below the inner ends of the slots 2, using in this step a tap having a slightly larger pitch diameter.

. This step is illustrated in Fig. 4. As a result of this operation, the thread on the inner faces of the segments I, while being a true continuasegments l inwardly in the radial direotion so. that they are permanently set in the positions shown in Fig. 5. By reason of this set, the inneri'aces of the segments converge toward the axis of the bore 6, so that the segments constrict the normal bore B and ofler an obstruction to the free passage of the nut on to the bolt. The inward displacement of the segments I may be nut.

effected in any suitable manner such for example, as that described in my aforesaid co-pending application. It is to be noted, however, that in the present instance, the outer surfaces of the segments i are undercut by an annular recess II which is of such character as to leave at the" outer ends of the segments and on the outer surfaces thereof a narrow shoulder II which form an abutment for the dies I by means of which the segments are inwardly displaced under pressure. This relativelynarrow contact area between the offsetting dies l5 and the segments I is desirable in order toinsure a uniform and accurately gauged degree of displacement. important, in order to obtain this effect, that the abutment shoulder ll embracing the entire series of segments I be accurately machined in the production of the blank so as to lie in exact concentricity with the a iis of the bore 6 of the This is more readily accomplished where the segments are formed as described with a narrow abutment shoulder.

In Fig. 6, the finished nut is shown applied to a bolt I, and it will be noted that the inner side edges 8 of the-segments l are free from the close engagement with the bolt surfaces that would result in the aforedescribed' undesirable scraping action. Kctually, the clearance need be very slight, and for ordinary purposes I have found that a pitch diameter in the thread of thesesments greater by .003" than. the pitch diameter of the normal thread in the bore 8 0f the nut will afford satisfactory results. This difference,

while ordinarily sumcient to effect the desired result,\does riot in any material degree adversely affect the locking function of the segments or the close frictional engagement between the sur- It is with respect to said body in radial direction,

1 the segments to faces of the segments and bolt upon which that solid wall of the nut body and resiliently movable threading the inner surface of said segment in continuation of the thread in the bore of the. nut and with a thread of somewhat greater pitch diameter, and subsequently inwardly displacing the segment to a normal position constricting said bore.

2. The method of manufacture, which consists in forminga nut having atone end a plurality nut and with a thread of somewhat greater pitch diameter, and subsequently inwar l displacing a normal positio constricting said bore. I

3. The method of manufacture, which consists in forming a nut having at one end an annular extension with a narrow external shoulder concentric with the nut axis and with longitudinal slots dividing said extension in a plurality of segments resiliently movable in radial direction, threading the inner surfacesoi said segments in continuation of the thread in the bore of the nut and with a thread of somewhat greatei pitch diameter, and subsequently exterting radial pressure on said shoulder to uniformly displace the segments inwardly to a normal position constricting said bore.

4. The method of manufacture which consists in slotting a nut longitudinally so as to form at one end a plurality of segments forming continuations of the solidwall of the nut body and resilientlymovable with respect to said body in radial direction, passing the nut over an elongated threaded mandrel to work off the burrs left by the slotting operation, rethreading the segmented end of the nut with'a-thread of some what greater pitchdiameter than the original thread, and subsequently inwardly displacing the segments to normal position constricting said bore.

' HARALD F. GADE. 

